PRIOR CONCURRENT THERAPY: Biologic therapy: At least 2 weeks since prior blood transfusions At least 2 weeks since prior growth factors At least 6 weeks since prior experimental vaccine therapy No prior immunotherapy for metastatic disease No concurrent anticancer immunotherapy Chemotherapy: No prior chemotherapy for metastatic disease No other concurrent anticancer chemotherapy Endocrine therapy: No concurrent anticancer hormonal therapy Radiotherapy: No concurrent anticancer radiotherapy except palliation for pain control or other reasons (e.g., bronchial obstruction or ulcerating skin lesions) with no curative intent Surgery: Not specified Other: At least 6 weeks since prior adjuvant or neoadjuvant therapy At least 4 weeks since prior experimental drugs At least 2 weeks since prior and no concurrent coumarin anti-coagulants, terfenadine, cisapride, cyclosporine, tacrolimus, theophylline, diazepam, sulfonylurea anti-diabetics, phenytoin, or carbamazepine No other concurrent experimental agents